The methanogenic communities and pathways in a high-temperature petroleum reservoir were investigated through incubations of the production water and crude oil, combined with radiotracer experiments and molecular biological analyses. The incubations were conducted without any substrate amendment and under high-temperature and pressurized conditions that mimicked the in situ environment (55°C, 5 MPa). Changes in methane and acetate concentrations during the incubations indicated stoichiometric production of methane from acetate. Rates of hydrogenotrophic methanogenesis measured using [(14)C]-bicarbonate were 42-68 times those of acetoclastic methanogenesis measured using [2-(14) C]-acetate, implying the dominance of methane production by syntrophic acetate oxidation coupled to hydrogenotrophic methanogenesis in the environment. 16S rRNA gene sequence analyses of the incubated production water showed bacterial communities dominated by the genus Thermacetogenium, known as a thermophilic syntrophic acetate-oxidizing bacterium, and archaeal communities dominated by thermophilic hydrogenotrophic methanogens belonging to the genus Methanothermobacter. Furthermore, group-specific real-time PCR assays revealed that 16S rRNA gene copy numbers of the hydrogenotrophic methanogens affiliated with the order Methanobacteriales were almost identical to those of archaeal 16S rRNA genes. This study demonstrates that syntrophic acetate oxidation is the main methanogenic pathway in a high-temperature petroleum reservoir.

Deep subsurface formations (for example, high-temperature oil reservoirs) are candidate sites for carbon capture and storage technology. However, very little is known about how the subsurface microbial community would respond to an increase in CO2 pressure resulting from carbon capture and storage. Here we construct microcosms mimicking reservoir conditions (55 °C, 5 MPa) using high-temperature oil reservoir samples. Methanogenesis occurs under both high and low CO2 conditions in the microcosms. However, the increase in CO2 pressure accelerates the rate of methanogenesis to more than twice than that under low CO2 conditions. Isotope tracer and molecular analyses show that high CO2 conditions invoke acetoclastic methanogenesis in place of syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis that typically occurs in this environment (low CO2 conditions). Our results present a possibility of carbon capture and storage for enhanced microbial energy production in deep subsurface environments that can mitigate global warming and energy depletion.

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Anaerobic methane-oxidizing archaea (ANME) are known to play an important role in methane flux, especially in marine sediments. The 16S rRNA genes of ANME have been detected in terrestrial freshwater subsurfaces. However, it is unclear whether ANME are actively involved in methane oxidation in these environments. To address this issue, Holocene sediments in the subsurface of the Kanto Plain in Japan were collected for biogeochemical and molecular analysis. The potential activity of the anaerobic oxidation of methane (AOM) (0.38-3.54 nmol cm⁻³ day⁻¹) was detected in sediment slurry incubation experiments with a (13) CH(4) tracer. Higher AOM activity was observed in low-salinity treatment compared with high-salinity condition (20‰), which supports the adaptation of ANME in freshwater habitats. The 16S rRNA sequence analysis clearly revealed the presence of a distinct subgroup of ANME-1, designated ANME-1a-FW. Phylogenetic analysis of the mcrA genes also implied the presence of the distinct subgroup in ANME-1. ANME-1a-FW was found to be the most dominant active group in the archaeal communities on the basis of 16S rRNA analysis (75.0-93.8% of total archaeal 16S rRNA clones). Sulfate-reducing bacteria previously known as the syntrophic bacterial partners of ANME-1 was not detected. Our results showed that ANME-1a-FW is adapted to freshwater habitats and is responsible for AOM in terrestrial freshwater subsurface environments.

Methylocaldum marinum sp. nov., a thermotolerant, methane-oxidizing bacterium isolated from marine sediments, and emended description of the genus Methylocaldum Genetic Research Section, Atmosphere and Ocean Research Institute, the University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8564, JapanAn aerobic, methane-oxidizing bacterium (strain S8 T ) was isolated from marine sediments in Kagoshima Bay, Japan. Phylogenetic analysis based on 16S rRNA gene sequences indicated that this strain is closely related to members of the genus Methylocaldum (97.6-97.9 % similarity) within the class Gammaproteobacteria. Strain S8 T was a Gram-staining-negative, non-motile, coccoid or short rod-shaped organism. The temperature range for growth of strain S8 T was 20-47 6C (optimum growth at 36 6C). It required NaCl (.0.5 %), tolerated up to 5 % NaCl and utilized methane and methanol. The major cellular fatty acid and major respiratory quinone were C 16 : 0 and 18-methylene ubiquinone 8, respectively. The DNA G+C content was 59.7 mol%. Strain S8 T possessed mmoX, which encodes soluble methane monooxygenase, as well as pmoA, which encodes the particulate methane monooxygenase. On the basis of this morphological, physiological, biochemical and genetic information, the first marine species in the genus Methylocaldum is proposed, with the name Methylocaldum marinum sp. nov. The type strain is S8 T (5NBRC 109686 T 5DSM 27392 T ). An emended description of the genus Methylocaldum is also provided.The methane cycle in the ocean has been the subject of increased attention in recent years. It has been reported that methane is produced not only in anaerobic environments but also in aerobic environments such as the water at the surface of the ocean, possibly through the decomposition of methylphosphonate (Karl et al. 2008) or via methanogenesis (Grossart et al., 2011). On the seafloor, destabilization of methane hydrate due to changes in ocean temperature has been found to occur in the North American margin (Phrampus & Hornbach, 2012), possibly 3Present address: Faculty of Science, Toyama University, 3190 Gofuku, Toyama-shi, Toyama 930-8555, Japan.4Present address: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo, Japan.Abbreviations: RuMP, ribulose monophosphate; sMMO, soluble methane monooxygenase.The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA, mmoX, pmoA and cbbL gene sequences of strain S8 T are AB894129, AB900160, AB900159 and AB922600, respectively.

Methyloceanibacter caenitepidi gen. nov., sp. nov., a facultatively methylotrophic bacterium isolated from marine sediments near a hydrothermal vent Department of Biological Science, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, JapanA moderately thermophilic, methanol-oxidizing bacterium (strain Gela4 T ) was isolated from methane-utilizing mixed-culture originating from marine sediment near a hydrothermal vent. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain Gela4 T was closely related to members of the genus 'Methyloligella' (94.7 % similarity) within the class Alphaproteobacteria. Strain Gela4 T was a Gram-staining-negative and aerobic organism. Cells were rod-shaped and non-motile. The temperature range for growth of strain Gela4

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Baseline erectile function greatly impacts cavernous nerve quantity and distribution. Cavernous nerve preservation in the neurovascular bundle, especially at the apex, is still essential for patients with erectile dysfunction.